While bringing mankind abundant material wealth, the development of the world also leads to the global ecological environment deterioration and causes a series of ecological problems, for example, the serious damage to vegetation such as forests and grasslands, water and soil loss, soil desertification aggravation, etc., which pose a grave threat to human survival and development. With the developing concept of the ecological environment and the increasing sustainable development requirements, the ecological management with plants as a main component has become an important technical approach to control the water and soil loss domestically and overseas. However, the restoration of ecosystems, such as exposed geotechnical surface and desertification or stony desertification land, is limited by the soilless or poor soil conditions, so that vegetation conditions need to be artificially provided. The main characteristic of the present vegetation restoration products is to combine plant seeds with functional carriers, so as to form roll products easy to plant artificially; the advantages lie in that the construction speed is fast and not limited by soil conditions. Whereas both the domestic and foreign relevant products have the common shortcomings such as single herb species added, low composite strength, poor structural stability, etc.
U.S. Pat. No. 5,226,255 discloses a vegetation blanket, the upper and lower parts of which are made of naturally degradable non-woven fibers. The middle layer that links the non-woven fiber layer is an apertured plastic mesh with high strength and two-way stability. The vegetation blanket includes seeds and may also include fertilizer and/or water absorbing material. This vegetation blanket can be laid on bare hillsides and reduce the soil erosion caused by runoffs.
U.S. Pat. No. 5,421,123 discloses a vegetation blanket that has a netty system and can prevent the loss of plant material. The vegetation blanket consists of soil improvement material, fertilizer, organic material and seeds, and forms a whole by bonding the upper and lower ribbons. The hole-like mesh can meet the requirements of plants germination and growth.
U.S. Patent no. 20090178334 discloses a vegetation blanket. The upper layer is made of fiber mesh with open grids to achieve a water penetration effect. The fibers extend to the grids so as to make seeds adhere to the fibers and stay in the grids. The lower layer is easy to absorb water and is composed of absorbent paper towel or spinning. The two layers of the vegetation blanket are both degradable materials.
Chinese patent CN201048485 slope greening vegetation blanket discloses a vegetation blanket. Evenly laid dry plant substrate is located between the upper layer mesh and the lower layer mesh made of jute or plastic. An integral blanket roll is formed by connecting upper and lower layers using stitch-bonding thread. There is also a layer of non-woven fabrics or degradable paper seed embryo between the lower layer mesh and the dry plant substrate, with evenly laid plant seeds adhered to the seed embryo.
At present, both the domestic and foreign ecological vegetation blankets have a certain role in water and soil conservation, with the advantages of simple manufacturing process, low maintenance, low cost, etc. However, there are also some deficiencies:
Firstly, with a small amount of substrate added, they can not be directly applied to vegetation restoration or greening of soilless interfaces. When they're used for vegetation restoration of rock slopes, slag fields, sandy lands, roofs, etc., the engineering surfaces must be covered with soil or artificial substrate before laying the vegetation restoration materials, therefore the construction cost is high.
Secondly, the solution to the control of water and temperature is simply covering with fiber, or filling with great amount of water retaining agent with seeds directly sprinkled into the water retaining agent. This will cause poor vegetation growth and can not achieve a good function of temperature and water control. Vegetation degradations tend to appear in case of extreme weather conditions, which will increase the engineering maintenance cost.
Thirdly, due to the above-described drawbacks, there are certain requirements for the environmental conditions of the vegetation blanket application, thus the application is limited to a small scope.